Pneumatic dispatch system



Nov. 6, 1934. c 5. JENNINGS El AL 1,979,801

PNEUMATIC DISPATCH SYSTEM Filed June 8, 1952 5 Sheets-Sheet 1 jnveiziar 666536? J: knwzrz qs' may:

Nov. 6, 1934- c. s. JENNINGS ET AL 15979,801

PNEUMATIC DISPATCH SYSTEM I 5 Sheets-Sheet 2 Filed June 8, 1932 17:061120715' fiwsier .52 Jerw'zz'nagni red 1? M66 yfl da w 5 Sheets-Sheet 3 Filed June 8, 1932 C. 5. JENNINGS ET AL PNEUMATIC DISPATCH SYSTEM Nov. 6, 1934.

Nov. 6, 1934.

c. 5. JENNINGS ET AL 1,979,801

PNEUMATIC DI SPATCH SYSTEM Filed June 8, 1932 5 Sheets-Sheet 4 'jiawiwni fikfisler i Jervzingqs al- J? aiae Nov. 6, 1934.

C. S. JENNINGS ET AL PNEUMATIC DISPATCH SYSTEM Filed June 8. 1932 fiwerzib r's kesi'er .5. Jerznuzgs 5 Sheets-Sheet 5 Patented Nev. 6, 1934 warren stares PATENT basics PNEUMATIC DISPATCH SYSTEM Massachusetts Application June 8, 1932, Serial No. 616,034

17 Claims.

This invention relates to an improvement in a pneumatic dispatch system of the minimum flow vacuum type, and more particularly to the power control apparatus by which the movement of the carrier impelling air flow is controlled.

Power control apparatus oi this general type is disclosed in the patent to Libby, No. 968,576, dated August 30, 1910, wherein are provided automatic pressure actuated means for initiating a carrier impelling air flow through the transmission tube whenever a carrier is entered therein, as well as means for cutting off such flow after the lapse of a predetermined period of time. While the patented device is regarded as generally correct in principle and highly effective in practice, we believe it preferable to have both the initiation and the cessation of carrier impelling air flow directly controlled by 29 the cairiers and accordingly to have the cessation of the air flow caused by. the discharge of the carrier from the delivery end of the tube rather than by the operation of a timing device.

This invention is a further development of the inventive concept embodied in the copending application of Fred R. Taisey,- Serial No. 475,167, filed August 14, 1930, which matured on June 21, 1932 into Patent No. 1,864,157, differing thereover in certain embodiments by the substitution of a closed pneumatic for the auxiliary valve which, when opened, placed the valve housing in direct communication with the atmosphere and in other embodiments by the provision of electrical means by which the air valve is locked in the closed position and opened when a carrier is inserted.

The primary object of this invention is to provide a power control apparatus of the minimum flow type wherein the insertion of a carrier causes the initiation of the opening of the air valve by pneumatic actuated means.

A further object of this invention is to provide in such apparatus pneumatic actuated means by which the air valve is normally locked in the closed position when the tube is not in use and by which that valve is released when the tube is in use, such means acting in response to the status of the air flow in the tube.

ther objects will appear from an examination of the following description and of the drawings which form a part thereof and in which Fig. 1 is a diagrammatic View illustrating a system embodying one application of this invention;

Fig. 2 is a sectionalview oi the valve mechanism with the parts in the positions which they occupy when the system is in use, one part being indicated by full lines in its normal position and by dotted lines in its abnormal position; 6

Fig. 3 is a view similar to Fig. 2 with the parts however in the positions which they occupy when the system is not in use;

Figs. 1, 5, 6, 7 and 8 illustrate, in sections, five forms of valve mechanisms in which the valve is locked in theopen position;

Fig. 9 is a side elevation and Fig; 10 a transverse section of a valve mechanism embodying another form of this invention wherein the closed valve is unlocked and impelled to the open position by electrically controlled means;

Fig. 11 is a side elevation partly in section of a valve mechanism embodying a form of this invention similar in function and operation to that shown inFigs. 9 and 10;

Fig. 12 is a bottom plan view thereof; and

Figs. 13 and 14, are enlarged views of a detail thereof, Fig. 14 being a sectional view of Fig. 13.

In Fig. l of the drawings is shown a fragmentary portion of the central station desk of a pneumatic dispatch system comprising transmission tubes such, for example, as the tube 11 which leads from the central station to a remote sending station and then back to the central station desk. Each tube 11 is provided with a delivery terminal 12 and an openended dispatch terminal 13 and is connected by a continuation 14 to a power control apparatus, indicated generally by the numeral 15, which, in turn is connected by a suction tube 16 to a vacuum drum or header 17 in which low pressure is continually maintained by means of a suitable exhauster, pump, or equivalent apparatus, not shown. A second continuation 18 leads to another tube (not shown). The above arrangement in general being old and well known in this art, further details thereof are believed to be unnecessary, the present invention being confined to improvements in the power control apparatus per se.

The power control apparatus shown in Figs.

2 and 3 comprises a substantially cylindrical valve housing 20 directly connected through a port 21 to the upper end of the suction tube 16 and through ports 22 carried by a fitting 23, here shown integral with the housing, to the continuations 14 and 18 of the transmission tubes. Pivotally mounted upon a shaft 24 supported in suitable bearings (not shown) in the that shown in Fig. 2, passes thereover.

wall of the housing 20 is a control valve which, when closed, as shown in Fig. 3, cuts off the connection through the housing between the suction tube 16 and the continuations of the transmission tubes and when open, as shown in Fig. 2, permits the free passage of air therebetween. The valve 25 is slightly unbalanced with reference to the shaft 24, the upper portion 26 being somewhat shorter than the lower portion 2'7, and furthermore, a flanged plate 28 is secured to the under surface of the portion 26 near the upper edge of the valve.

The housing 20 is closed at its upper end by a cap 30 and at its lower end by a pneumatic 31 suitably secured thereto. may be of any well known type being here shown as comprising a two-part casing 32 divided by a diaphragm 33 into two chambers 34 and 35. The chamber 34 is in direct communication at all times with the atmosphere through a port 36 while the chamber is similarly in communication with the housing 20 through a port 37. The diaphragm 33 is centrally reinforced by plates 38 and 39 and to its. center is attached a pin 40 the lower end of which extends through and is guided by a sleeve 41 here shown as integral with the lower part of the casing 32. A spring 42 surrounding the pin and sleeve normally tends to draw the pin and diaphragm into the position shown in Fig. 3. The pin is attached to the diaphragm by nuts 43, 44 and its enlarged upper end 45 projects into the chamber 35 for a purpose to be described later.

Mounted upon the plate 39 by suitable means is a strap 46 which may, as here shown, be U-shaped in cross section and through which the upper end of the pin 40 may pass. Pivotally supported upon the strap 46 is a trip bar 47 which extends into the housing 20 and is guided by a slotted plate 48 projecting from one wall of the housing. A spring 49 normally acts to hold the bar 4'7 in the upright position shown in full lines in Fig. 2. A latch bar 50 pivotally mounted intermediate its length upon a pin 51 acts to hold the valve 25 closed as shown in Fig. 3. One end of the bar terminates in a tongue 52 adapted when the valve is closed to enter a recess 53 therein. The other end of the bar projects above the upper end 45 of the pin 40 and is preferably weighted so that the latch bar is normally held in the position shown in Fig. 3. It will be noted that the bar 50 extends below the valve 25 and that the valve, as it moves from the position shown in Fig. 3 to Extending below the bar 50 is a deflector 54 into contact with which the bar is brought by the pin 40 when the valve is released.

The minimum flow is provided in the i1- lustrated embodiment by means of a by-pass formed by a pocket 55 connected by a port 56 with the interior of the housing at one side of the valve 25 and connected by a channel 5'7 with the interior of the housing at the other side of the valve. A set screw 58 is provided to regulate the amount of minimum flow through the by-pass.

The operation of the device illustrated in Figs. 2 and 3 will now be described, it being assumed that the parts are in the position shown in Fig.

3 at which time the system is at rest and only a minimum flow of air is traveling therein. When a carrier is inserted in the dispatch terminal of a transmission tube the supply of air to the system by that tube is cut off. As a re- The pneumatic sult a vacuum or minus pressure is set up in the housing 20 causing an unbalancing of the diaphragm 33 of the pneumatic 30 so that the atmospheric pressure in the chamber 34 acts to raise the diaphragm against the tension of the spring 42. This movement of the diaphragm causes the end 45 of the pin 40 to strike the end of the latch bar 50 and release the valve 25 while the trip bar 4'7 strikes the plate 28 and initiates the opening of the valve which there upon takes the position shown in Fig. 2 so that a full carrier impelling flow is set up. The surge of air into the housing set up when the carrier is discharged impacts upon the lower end 2'7 of the valve 25 and swings it into the position shown in Fig. 3. As the valve approaches that position the upper end 28 thereof swings the tip of the trip bar 47 into a recess 60 in the wall 61 separating the housing and fitting as shown in dotted lines in Fig. 2, such movement being permitted by the slot in the plate 48 and by the spring 49. At the same time the diaphragm 33 of the pneumatic 30 is depresesd by the action of the spring 42, since the pressure on the oppcsite sides is now substantially balanced and the upper end 45 of the pin moves from the latch bar 50 so that when the valve 25 reaches the closed position shown in Fig. 3, the bar will move in front of the valve and hold it in place. The diaphragm as it is depressed also lowers the bar 4'7 until it is free to take the position shown in Fig. 3.

The embodiments shown in Figs. 4, 5 and 6 are based upon the embodiment previously described but include means for insuring a positive movement of the diaphragm 33 to prevent it from fluttering and also means for locking the air valve 25 in the open position.

In Fig. 4 a double acting pilot valve '70 is mounted in the casing 32 of the pneumatic through which the compartment 35 may be in communication with the atmosphere. The compartment 34 is at all times in connection with the atmosphere through the port 36. The valve '70 comprises a tube '71 open at both ends, adapted to be closed at the inner end i. e. that end within the compartment 35, by a plate 72 which is yieldably held in the closed position by a spring '73 bearing against the plate 39 when the diaphragm 33 is raised. A pin '75 secured to the plate 39 projects through the plate 72 and is provided with an enlarged end or nut '76 which when the diaphragm 33 is depressed, bears against the plate '72 to move it away from and open that end of the tube '71. The outer end of the tube 71 is adapted to be closed by a plate '78 mounted on a stem '79 pivotally supported from an arm pivoted at one end to an ear 81 in the wall of the fitting 23. The free end of the arm 80 extends toward the air valve 25 and terminates between the trip 4'7 and a post 82 fixed upon and carried by the strap 46. Stop screws 83,

84 are adjustably mounted on the post 82 and as the diaphragm is raised or depressed, engage the end of the arm 80 to move it in the desired direction.

Mounted on the end 2'7 of the air valve 25 is a hook 85 adapted to be engaged by a latch 86 mounted upon a rock shaft 8'7 supported in the wall of the casing 20. As indicated in dotted lines the latch 86 is normally held in the position shown in Fig. 4 by an arm 88 secured to the shaft 87 outside the casing. Mounted on the shaft 87-is a vane 89 located in the path of travel of the air through the housing.

The control apparatus is shown in Fig. 4 in the position in which a full carrier impelling flow of air is set up in the system. When the carrier is discharged a surge of air set up' through the system strikes the vane 89 causing the shaft 87 to rock and the latch 86 to release the air valve and impacts upon the end 27 of the airvalve to swing it into the closed position. This change in the condition of the air in the housing 20 also unbalances the diaphragm 33 so that the spring 42 can act to move the diaphragm downwardly, which movement of the diaphragm, of course, lowers the strap 46 and the post 82 carried thereby. The pin engages the plate 72 of the pilot valve 70 so that the diaphragm in the pneumatic is now directly subjected to atmospheric pressure on either side. This opening of the tube 71 is only momentary, the tube being again closed by the plate 78 which is drawn down by the coaction of the pin 84 on the post 82 with the arm 80. The admission of atmospheric air for'this short period, however, is sufiicient to stabilize the diaphragm 33 and prevent any fluttering thereof. When the valve 25 is closed and a carrier is inserted into the line the apparatus operates in substantially the manner previously disclosed with respect to the first embodiment. It will be understood, however, that as the diaphragm 33 is raised, the'pin 83 of the post 82 raises the arm lifting the plate 78 from the outer end of the tube 71 and the spring 73 raises the plate 72 against the inner end thereof. The parts are so adjusted that the tube is opened only for a short space of time if at all. It will be understood that this movement of the diaphragm also causes the latch 50 to release and the trip 47 to open the air valve 25 and so that the parts may take the position shown in Fig. 4, in which the valve is held by the coaction of the latch 86 and the book 85.

In the modification shown in Fig. 5 the air valve 25 is held in the open position by the coaction of the hook 85 and the latch 86 in the manner previously described and the pneumatic is constructed and functions as in the first described embodiment. In place of the pilot valve 70 shown in Fig. 4 there is, however, provided a pilot valve 100 including a tube 101 open at both ends and extending through the wall of the fitting 23. The outer end of the tube 101 may be closed by a plate 102 carried by a stem 103 mounted upon guides 104 supported at the center of the tube 101, a spring 105 acting to hold the plate 102 normally in contact with the end of the tube 101. Mounted in the fitting 23 is a post 106 which carries a pin 107 to which are secured the arms 108 and 109. The free end of the arm 108 normally bears upon the end of the stem 103 of the plate 102 while the free end of the arm 109 is positioned to contact with a pin 110 carried by the trip bar 47. The operation of this unit need not be described in detail. It will be apparent that when the diaphragm 33 is raised upon the insertion of a carrier in the system, the pin 110 on the trip bar 47 will strike the arm 109 rotating the shaft 107 and causing the arm 108 to bear on the stem 103 and force the plate 102 to leave the end of the tube 101 against the urge of the spring 105, so that the housing is directly connected with the atmosphere during the travel of the carrier. The

surge set up when the carrier is discharged causes the vane 89 to release the air valve 25 and acts upon the end 27 of the valve toswing it into the closed position. The depression of the diaphragm 33 as previously described permits the spring 105 to act upon the plate 102 and close the valve 100.

The embodiment shown in Fig. 6 is similar in function to those previously described and more particularly to that shown in Fig. 5. .The pilot valve 110, however, comprises the open ended tube 111 which extends through one wall of the fitting 23 normally closed at its inner end by a plate 112 carried by an arm 113 pivotally supported upon ears 114 secured to the tube 111, and normally held in the valve closing position by a spring 115. The free end of the arm 113 extends into the path of a pin 116 carried by the trip bar 4'7. It is obvious that in the manner previously described the upward movement of the trip bar 47 by the diaphragm 33 will cause the plate 112 to open the valve 110 and connect the housing directly with the atmosphere. The air valve 25 of this embodiment is secured in the open position by an arm 120 pivotally supported upon a pin 121. A weight 122 fixed upon one end of the arm 120 causes the parts normally to take the position shown in Fig. 6. Secured to the arm 120 is a vane123 located in the path of travel of the air and caused to function, as will be describedlater, in the same manner as the vanes 89. The movement of the arm 120 about the pin 121 is guided by a pin 125 on which the latch 50 is pivoted and a slot 126 in the arm through which slot the pin 125 extends. The arm 120 is provided with a shoulder 127 so shaped and located that when the Valve is opened it bears against the edge of the valve and holds it in such position as shown in Fig. 6. The surge of air set up by the discharge of the carrier in the system acts upon the vane 123 to swing the arm 120 about the pin 121 releasing the air valve 25 which, as previously described, is swung by the surge into the closed position and secured therein by the latch 50. When the unit is at rest and the carrier is inserted into the system the pneumatic operates as previously described and the air valve 25 is swung into the open position in which it is secured by the arm 120, the pilot valve 110 being also opened by lifting the plate 112.

The embodiments shown in Figs. 7 and 8 cmbody other means for connecting the compartment 35 with the atmosphere similar to the pilot valves already shown and described. In each of these embodiments the air valve 25 is opened by the action of a post 130 carried by the diaphragm 33 and constituting substantially an extension of the pin 40. Mounted on one face of the end 26 of the air valve is a plate 131 having an arcuate slot 132 adapted to receive a pin 133 carried by a bracket 134 mounted on the partition 135 between the main housing 20 and the fitting 23. The end of the plate 131 is engaged by the upper end of the post 130 when the diaphragm in the manner previously described is raised to the position shown in Figs. 7' and 8 by the insertion of a carrier into the system, so that the post 130 during such movement opens the valve 25. At the same time the post 130 also acts upon a latch 136 which is similar to the latch 50 previously described and causes that to release the valve 25 so that it can assume the open position. In

each of these embodiments the valve 25 bears, when closed, upon a ridge 137 here shown as integral with the wall of the housing 20. One object of each of these embodiments is to pro vide a connection to the atmosphere from the compartment 35 when the air valve 25 is open, whereby the diaphragm is balanced and resumes its normal position shown by dotted lines. The pilot valve 140 of the embodiment'shown in Fig. 7 comprises a housing 141 having a chamber 142 in which reciprocates an arm 143, piv-. otally supported intermediate its ends upon a pin 144. One end 145 of the arm extends through the housing into a recess defined by the plates 146 and 147 projecting from the post 130. The chamber 142 is connected to the atmosphere by a port 150 and to the interior of the housing by a port 151. The center of the end 152 of the arm 143 is hollow, as indicated in dotted lines and forms a conduit connecting either of these ports with the center of the hollow pin 144 on which the arm 143 is pivoted which center is at all times connected to the compartment 35 by a port 153. When the valve is closed the compartment is connected to the interior of the valve housing 20. The insertion of a carrier into the system causes the diaphragm 33 to take the full line position by reason of the change in status of the air previously described, and the post 130 to open the valve 25. The. valve opening movement of the post also causes the arm 143 to connect the compartment 35 to the atmosphere through the port '153, the hollow pin 144 and the passage 152 in the arm 143. When the carrier is discharged from the system the surge acts in the manner previously described upon the end 27 of the valve swinging that valve into the closed position shown in dotted lines in Fig. 7 in which it is held by the latch 136. As the valve moves, the diaphragm 33, if raised, is caused to descend by the contact of the plate 131 and post 130, shifting the arm 143 from the position shown in full lines toward the position shown in dotted lines. It will be noted that this movement of the diaphragm 33 is initially facilitated by the fact that the compartments 34 and 35 are open to the atmosphere whereby the diaphragm is balanced and the spring 42 tends to cause the diaphragm to descend. When the diaphragm has descended to its lowest position the arm 143 has been swung by the action of the plate 146 so that the compartment 35 is connected to the interior of the housing 20 by the port 153, the center of the pin 144, the passage 152 in the arm and the port 151.

The embodiment shown in Fig. 8 differs from that shown in Fig. 7 by the substitution for the pilot valve 140 controlled by the diaphragm of a pilot valve 160 controlled by the status of the air in the system. This valve comprises a housing 161 having a chamber connected to the compartment 35 by ports 162 and 163, to the housing 20 by a port 164, and to the atmosphere by a port 165. Pivotally mounted in the chamber and substantially filling the same is a cylindrical block 166 having a passage 167 extending transversely through the center thereof. Secured at one end of the block 166 is an arm 168 which carries a vane 169 located in the path of the air through the apparatus. When the air valve 25 is opened as shown in Fig. 8 by the insertion of a carrier as previously described the vane 169 is moved by the carrier impelling flow of air into the position shown in full lines so that the compartment 35 is connected to theatmosphere through the port 163, the passage 167 and the port 165 and the spring 42 moves the diaphragm into the dotted line position. When the carrier is discharged from the system the surge of air acts upon and closes the valve 25. The vane 169 moves by gravity into the dotted line position causing the block 166 to rotate so that the compartment 35 is now connected with the housing 20 by the port 162, the passage 167 and the port 164. When a carrier is inserted the diaphragm will respond to the change in status of the air.

In the embodiment shown in Figs. 9 and 10 the air valve 25 is actuated by a solenoid plunger 170. The valve 25 is secured in its closed'position as here shown by a latch 171 pivoted intermediate its ends upon a pin 172 and normally held in the operative position by a weight 173. The end 174 of the arm is connected by a link 175 with the plunger 170, while mounted upon the end 176 is a trip bar 177 which supports the weight 173 and which reciprocates througha guide bracket 178 and is adapted to engage the clip 28 on the end 26 of the valve 25. Mounted upon the control housing is a pneumatic 180 comprising a diaphragm 181 which forms a portion of the wall of the fitting 23 and a cup-likehousing 182 open at all times to the atmosphere through a port 183. The energizing or deenergizing of the solenoid 185 is controlled by any suitable means as for example a battery 186. connected to one side of the solenoid by a lead 187 and connected by a lead 188 to one leg 189 of a jack in the housing 182. The other leg 190 of the jack is connected by a lead 191 with the leg 192 of a jack mounted on the outer wall of the housing 20. The other leg 193 of this jack. is connected by a lead 194 with the solenoid 185. The contacts between the legs 192 and 193 of the jack on the wall of the housing are normally open and are closed, when the valve 25 is closed, by the action of a pin 195, carried by an arm 196 fixed to the shaft 24 on which the valve 25 is mounted. The contacts between the legs 189 and 190 of the jack in the compartment 182 of the pneumatic 186 are normally open being held separated by a button 197 carried upon the inner face of the diaphragm 181.

When a carrier is inserted into the system the condition of the air in the housing will be upset in the way previously described. The suction so produced causes the diaphragm 181 to shift from the full line position of Fig. 10 into the dotted line position, thus permitting the contacts carried by the legs 189 and 190 to close and complete the circuit energizing the solenoid 185 and causing the plunger 170 to shift from the full to the dotted line position shown in Fig. 10. This movement of the plunger 170 causes the latch 171 to release the air valve 25 and at the same time causes the trip bar 177 to impel it into the open position shown in dotted lines in Fig. 10 the valve 25 being released by the latch before the bar 177 acts upon it. The valve is further urged to assume this position by the action of the weighted arm 198 mounted on the shaft 24. When this movement of the arm takes place the legs 192 and 193 of the jack on the housing separate, breaking the circuit and deenergizing the solenoid so, that the latch 171 and bar 177 will resume the position shown in full lines in Fig. 10. When the carrier is discharged from the system the surge of air acting on the end 27 of the valve 25 causes that valve to return to the full line position in which it is secured by the latch 171. This movement of the valve of, course causes the pin 195 to closethe contacts of the legs 192 and 193 of the jack and at the same time the diaphragm 181 will be caused to resume the position shown in full lines in Fig. 10, so that the legs 189 and 190 of the jack in the pneumatic are separated.

The embodiment shown in Figs. 11, 12, 13 and 14 is similar to that just described since it employs electrical control circuit and a solenoid. The power control unit here disclosed is similar in many respects to that previously described and will not therefore be discussed in detail. So far as possible, however, the reference numerals used in the other figures will be applied with primes afixed thereto. The air valve 25' in the housing is carried by a shaft 24 and under normal conditions through the action of the weighted arm 198 would assume the open position. It is held from such position, however, by thejengagement of a latch 200 with a clip 201 secured to the end 26 of the air valve. The clip 201 is so formed that when the valve is closed it will rest upon the lowershoulder 202 of a recess 203 formed in the partition 135' between the housing 20' and the fitting 23. The housing 20' has a port 205 open to the atmosphere and adapted to be closed by a clapper 206 pivotally connected at one end to the housing by a hinge 207. The clapper 206 is normally open, resting at its free end upon an adjustable pin 208 carried by a bracket 209 secured to the housing 20. The partition 135' is normally recessed as shown particularly in Fig. 11 to provide a chamber 210 which receives a link 211 secured to and carried by a plunger 212 of a solenoid 213. The latch 200 is mounted in a slot 214 formed in the link 211 being pivoted upon a pin 215 and free to swing around that pin between limits determined by a wall 216 and a pin 217. .When the air valve is closed and the solenoid 213 deenergized as shown in Fig. 11 the link 211. descends so that the latch 200 will rest against the clip 201 holding it against the shoulder 202 and thus securing the. valve 25 in the close position.

Pivotally mounted upon a pin 220 on'the outer factv of the housing adjacent the port 205 is a lever 221 normally held by a weight 222 in contact with a set screw 223 in an car 224 on the housing. The screw 223 is suitably insulated from the ear 224 and the housing. Projecting from the clapper 205 is an arm 225 carrying a set screw 226 suitably insulated therefromand adapted under certain conditions to engage the arm 221. The solenoid 213 is electrically controlled by any suitable means, as for example the battery 230, connected at one end by a lead 231 with the solenoid 213 and at the other end by a lead 232 through a switch 233 with the pin 226.

@ suction is created in the housing 20 the clapper 206 will be drawn to close the port 205. This movement of the clapper brings the screw 226 and the contact with the arm 221 and thus completes the circuit from the battery 230 through the solenoid 213, energizing the solenoid and raising the link 211 so that the air valve 25 is released from the latch 200. At the same time the link strikes the valve 25 initiating its opening movement under the action of the weighted arm 198'. As the clapper 206 continues to close,

however, the screw 226 bearing against the arm 221 causes it to swing on its pivot pin 220 thus breaking the contact between the arm and the screw 223 and deenergizing the solenoid so that the parts Will resume the position shown in Fig. 11 with the exception, of course, that the air valve 25' will remain in the open position. When the carrier is discharged from the line the surge of air'set up by such discharge causes the air valve 25 to return to the position shown in full lines in Fig. 11 and be held therein by the latch The clapper 206 will at the same time open and while it will complete the circuit previously described this completion will be only momentary and will not disturb the position of the air valve 25.

We claim:

1. In a pneumatic dispatch system, a power control of the minimum fiow type comprising a housing, a closed pneumatic connected on one side to the interior of the housing, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling flow of air, a by-pass which provides a minimum flow of air when the valve is in the first named position, and means for locking the valve in one of said positions which means are rendered inoperative by said pneumatic in response to a change in the status of the air in the system.

2. In a pneumatic dispatch system, a power control of the minimum fiow type comprising a housing, a closed pneumatic connected on one side to the interior of the housing, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling flow of air, a by-pass which provides a minimum how of. air when the valve is in the first namedposition, and means for locking the valve in such position, which means are rendered inoperative by said pneumatic in response to the change inthe status of the air in the system caused by the introduction of a carrier.

3. In a pneumatic dispatch system, a power control. of the minimum flow type comprising a housing, a closed pneumatic connected on one side to the interior of the housing, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling flow of air, a by-pass which provides a minimum fiow of air when the valve is in the first named position, means for initiating the movement of the valve from one position to the otherrposition which means are caused by said pneumatic to act in response to a change in the status of the air in the system, and means for locking said valve in the first position which means are rendered inoperative by the pneumatic upon the introduction of a carrier into the system.

4. In a pneumatic dispatch system, a power control of the minimum fiow type comprising a housing, a closed pneumatic connected on one sideto the interior of the housing, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling flow of air, a by-pass which provides a minimum flow of air when the valve is in the first named position, means for initiating the movement of the valve from the first position to the second position which means are caused by said pneumatic to act in response to the change in the status of the air in the system caused by the introduction of a carrier, means for locking the valve in the first position which means are rendered inoperative by said pneumatic upon such change in status in the air.

5. In a pneumatic dispatch system, a power control of the minimum flow type'comprising a housing, a closed pneumatic connected on one side to the interior of the housing, an air valve in the housing which in one position prevents and in the other position permits a carrier impolling flow of air, a by-pass which provides a minimum flow of air when the valve is in the first named position, and means for initiating the movement of the valve from the first position to the second position which means are advanced intov initiating contact with the valve by the pneumatic in response to the change in the status of the air in the system caused by the introduction of a carrier and are retracted from such contact by the pneumatic in response to the change in the status of the air in the system caused by the discharge of such carrier.

6. In a pneumatic dispatch system, a power control of the minimum flow type comprising a housing, a closed pneumatic connected on one side to the interior of the housing, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling flow of air, a by-pass which provides a minimum flow of air when the valve is in the first named position, a latch bar for holding the valve in such position and a trip bar for initiating the movement of said valve from such position to the other position, said latch bar being rendered ineffective and said trip bar being caused to act by said pneumatic in response to the change in the status of the air in the system caused by the introduction of a carrier.

'7. In a pneumatic dispatch system, a power control of the minimum flow type comprising a housing, a closed pneumatic connected on one side to the interior'of the housing, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling fiowof air, a by-pass which provides a minimum flow of air when the valve is in the first named position, a diaphragm in said pneumatic, a latchibar for holding the valve in such position and means for initiating the movement of said valve from such position to the other position, which means includes a trip bar supported upon said diaphragm and brought into. contact with said valve in response to the change in the status of theair in the system caused by the introduction of a carrier.

8. In a pneumatic dispatch system, a power 'i control of the minimum flow type'comprising a housing having a port therein, a pneumatic closing said port at all times, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling flow of air, a by-pass which provides a minimum fiow of air when the valve is in the first named position, a diaphragm in said pneumatic, and means for initiating the movement of said valve from such position to the other position, which means includes a trip bar supported upon said diaphragm and brought into contact with said valve in response to the change in the status of the air in the system caused by the introduction of a carrier.

9. In a pneumatic dispatch system, a power control of the minimum flow type comprising a housing having a port therein, a pneumatic closing said port, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling flow of air,

a by-pass which provides a minimum flow of air when the valve is in the first named position, said pneumatic comprising a casing and a diaphragm dividing the interior of said casing into two compartments, one of which is open at all times to the atmosphere, means carried by the diaphragm for initiating the movement of said valve from such position to the other position in response to the change in the status of the air in the system caused by the introduction of a carrier and a pilot valve through which the other compartment of the casingis connected to the atmosphere as the movement of the valve is initiated.

10. In a pneumatic dispatch system, a power control of the minimum flow type comprising a housing having a port therein, a pneumatic closing said port, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling flow of air, a by-pass which provides a minimum flow of air when the valve is in the first named position, and means for locking the air valve in both said positions which means are released upon the change in the status of the air in the system.

11. In a pneumatic dispatch system, a power control of the minimum flow type comprising a housing having a port therein, a pneumatic closing said port, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling flow of air, a by-pass which provides a minimum fiow of air when the valve is in the first named position, means for locking the air valve in the first named position which means are rendered inoperative by the pneumatic in response to the change in the status of the air in the system caused by the introduction of a carrier and means for locking the air valve in the second named position which means are rendered inoperative by the surge of air set up in the system upon the discharge of a carrier.

12. In a pneumatic dispatch system, a power control of the minimum flow type comprising a housing having a port therein, a pneumatic closing said port, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling flow of air, a by-p'ass which provides a minimum flow of air when the valve is in the first named position, a pilot valve in said housing comprising a tube through which the interior of the housing is connected to the atmosphere, a plate normally adapted to close one end of the tube and means actuated by said pneumatic when a car rier is introduced into the system for causing the plate to open the tube.

13. In a pneumatic dispatch system, a power control of the minimum flow type comprising a housing having a port therein, a pneumatic closing said port, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling flow of air, a by-pass which provides a minimum fiow of air when the valve is in the first named position, a pilot-valve in said housing comprising a tube through which the interior of the housing is connected to the atmosphere, a plate normally adapted to close one end of the tube, said pneumatic including a diaphragm, and means actuated by the diaphragm in response to the change in the status of the air in the system caused by the introduction of a carrier for causing the plate to open the tube.

14. In a pneumatic dispatch system, a power control of the minimum flow type, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling flow of air, means for locking the valve in the first named position and electrical means for rendering said locking means inoperative in response to the change in status of the air in the system caused by the introduction of a carrier.

15. In a pneumatic dispatch system, a power control of the minimum flow type, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling flow of air, means for locking the valve in the first named position and electrical means for rendering said locking means inoperative in response to the change in status of the air in the system caused by the introduction of a carrier, said electrical means including a solenoid, an electric circuit normally open and means actuated by said change in status for closing said circuit whereby the solenoid is energized to render the locking means inoperative.

16. In a pneumatic dispatch system, a power control of the minimum flow type, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling flow of air, means for locking the valve in the first named position, means for initiating the movement of the valve from that position to the second named position and electrical means for rendering said locking means inoperative and said initiating means operative in response to the change in status of the air in the system caused by the introduction of a carrier.

17. In a pneumatic dispatch system, a power control of the minimum flow type, an air valve in the housing which in one position prevents and in the other position permits a carrier impelling flow of air, means for locking the valve in the first named position, means for initiating the movement of the valve from that position to the second named position and electrical means for rendering said locking means inoperative and said initiating means operative in response to the change in status of the air in the system caused by the introduction of a carrier, said electrical means including a solenoid, an electric circuit normally open and means actuated by said change in status for closing said circuit whereby the solenoid is energized to render the locking means inoperative and the initiating means operative.

CHESTER S. JENNINGS. FRED R. TAISEY. 

